Theses and Dissertations at Montana State University (MSU)
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Item Developing bio-inspired methodologies for encoding angular position from strain(Montana State University - Bozeman, College of Engineering, 2020) Lange, Christopher William; Chairperson, Graduate Committee: Mark JankauskiAs mechanical systems rely more on closed-loop control, the sensors which supply feedback information are essential. Additionally, in systems where sensor function is critical, sensor redundancy is important to retain functionality if one or more sensors fail. Redundancy can be achieved through multiple high-fidelity sensors which measure the same type of information, such as gyroscopes or accelerometers. However, multiple high-fidelity sensors can increase cost significantly. This thesis explores the potential to replace or augment the functionality of angular position sensors using strain measurements. Strain gauges are already used in system health monitoring systems. By utilizing these already implemented sensors to measure angular position, we can remove the additional cost of redundant angular position sensors. However, for complex systems, the mapping between strain and angular position is unclear. By incorporating reduced order, physics-based models into machine learning techniques, we can efficiently transform high-order strain data into angular position. To demonstrate the potential of using alternative sensing methods, we developed a reduced order model of a parametrically excited flexible pendulum. Inspiration for this simplified system comes from insect halteres, which are small sensory organs evolved from insect hind wings which provide rapid information about body rotation. The parametrically excited flexible pendulum allows a single axis of rotation and single direction of flexibility to be paired, and their relationship studied. By varying parameters within the model such as pendulum length and modulus as well as parametric excitation amplitude and frequency, the Gaussian process regression learning can be optimized to reduce training time and increase untrained prediction accuracy. Inputs of strain and parametric excitation position along with their respective first and second derivatives are then analyzed to determine which inputs are interrelated and therefore un-necessary, thus reducing the input required. This provides the essential first steps towards using machine learning to implement multiple sensor, deformation based, multi axial angular position sensing in complex systems.Item Towards a precision measurement of the Newtonian constant of gravitation and accelerometry with a levitated microsphere in a magneto-gravitational trap(Montana State University - Bozeman, College of Letters & Science, 2020) Lewandowski, Charles Wayne; Chairperson, Graduate Committee: Brian D'UrsoSince the theory of gravity was published by Issac Newton in the seventeenth century, scientists have studied its strength, originally for the purpose of astronomy and measuring the density of the Earth. After centuries of research and measurements, G remains the least precisely known fundamental constant. A new method for a time-of-swing measurement of G, developed a the National Bureau of Standards 1930, is proposed using a levitated microsphere in a magneto-gravitational trap. A new magneto-gravitational trap based on a previous system from our laboratory has been developed for a measurement of G. This trap has been designed to load large particles with low oscillation frequencies with large amplitudes of motion to improve sensitivity to G. Because of the weak trap, a loading method has been developed utilizing electric fields to help balance the force of gravity. A stable and variable high voltage reference has been developed to provide the necessary electric field. Camera-based feedback control has been implemented for cooling the center-of-mass motion or heating the motion in a controlled way. To limit errors due to equilibrium shifts of the particle in the trap from tilt, a simple modification was made to an optical table to actively stabilize the tilt. A measurement of G requires high sensitivity to accelerations and forces. The parameters achieved towards the measurement of G makes this system sensitive to acceleration. The first direct use of a room temperature levitated optomechanical system as an accelerometer has been achieved, with the best sensitivity to accelerations of any room temperature levitated optomechanical system. The sensitivity was measured to be 3:6 x 10 -8 g / square root of Hz.Item Development of an economic, mobile, dual oxygen and pH sensor(Montana State University - Bozeman, Graduate School, 2016) Hall, Jacqueline Paige; Chairperson, Graduate Committee: Peggy Taylor.Optical pH and oxygen sensors have various advantages over Clark amperometric oxygen electrodes, including portability and utility in aqueous environments unsuitable for the Clark electrode. The goal of this study was to affordably develop a dual pH and oxygen-sensing probe that could be used in a variety of settings. This study resulted in the development of the oxygen-sensing component of such a device. This component consisted of Platinum (II)-meso-tetra (2,3,4,5,6-pentafluorophenyl) porphyrin (PtTFPP) suspended in a polystyrene-based matrix. A 405 nm LED excited the PtTFPP phosphorescence and a Hamamatsu Digital Color Sensor S11012-01CR recorded the resultant emission intensities of the porphyrin. A code was written for an Arduino Uno ® microcontroller, to control the LED and color sensor, while recording the appropriate data. The oxygen-sensing component showed expected oxygen sensitivity during oxygen depletion studies.Item Design, fabrication, and testing of the van der Paw piezoresistive structure for pressure sensing(Montana State University - Bozeman, College of Engineering, 2008) Cassel, Robert Douglas; Chairperson, Graduate Committee: Ahsan MianThe project characterizes a piezoresistive sensor under variations of both size and orientation with respect to the silicon crystal lattice for its application to MEMS pressure sensing. The sensor to be studied is a four-terminal piezoresistive sensor commonly referred to as a van der Pauw (VDP) structure. The VDP sensor is used primarily in sheet resistance measurements, but has also been determined to be useful in determining the stress components at a point on (100) and (111) silicon wafer surfaces. In a previous study, our team has determined the relation between the biaxial stress state at a point and the piezoresistive response of the VDP by combining the VDP resistance equations with the equations governing silicon piezoresistivity. It was found that the theoretical sensitivity of the VDP sensor is over three times higher than the conventional filament type resistor. With MEMS devices being used in applications which continually necessitate smaller size, understanding the effect of size on VDP performance is important. In order to test the validity of the theoretical calculations which were done by our group, appropriate devices were manufactured on a (100) silicon test wafer. The wafer was designed to have numerous pressure sensitive diaphragms which can reliably sustain a pressure difference of approximately 50kPa. Each diaphragm was doped with a VDP or other sensor designed to test the sensitivity of the VDP vs. a certain parameter. These parameters include size, misalignment, and diaphragm position, in addition to the comparison of sensitivity to conventional sensor types. A test strip was also included in the design in order to determine an empirical relationship between stress and resistance. In testing the VDP devices for comparison with conventional sensor types, it was found that the VDP devices had a linear response as expected, were the most sensitive, and provided a number of additional advantages. Specifically, the VDP device allows for significant miniaturization, because its resistance value is independent of size, and the measurement technique is independent of line resistance. The simple geometry of the VDP also simplifies fabrication.Item Chemical sensors and instrumentation powered by microbial fuel cells(Montana State University - Bozeman, College of Engineering, 2007) Angathevar Veluchamy, Raaja Raajan; Chairperson, Graduate Committee: Joseph D. Seymour; Zbigniew Lewandowski (co-chair)The use of microbial fuel cells to power electronic devices is inhibited by their low voltage and current outputs, therefore they cannot be used directly to power electronic devices without appropriate power management. The goal of the thesis is to power chemical sensors but currently there are no available sensor circuitries which can be operated at the low potential and current delivered by a microbial fuel cell. In this thesis, novel sensor circuitry and power management circuitry have been developed. The sensor circuitry can be programmed to operate any generic amperometric sensor and the data is accessible using wireless communication. The power management circuitry boosts the low potential and current outputs of a microbial fuel cell to the higher level required for powering the sensor circuitry. For testing purposes, the sensor circuitry was programmed to operate a chemical sensor measuring copper and lead concentrations in water. This work has demonstrated that by adopting the proposed power management and sensor circuitry, the energy from a microbial fuel cell can be used for powering electronic devices, including chemical sensors deployed at remote locations.Item Wireless sensor interrogator design for passive, resonant frequency sensors using frequency modulation spectroscopy(Montana State University - Bozeman, College of Engineering, 2009) Peterson, Brian James; Chairperson, Graduate Committee: Todd KaiserThe lack of passive, wireless, chemical and biological sensor systems is a significant impediment to sensor system applications. While active sensors with a wireless communications link continue to decrease in power consumption, they still require a power source, such as a battery. This active power consumption limits the useful life of the sensor and its applications. A more attractive solution would be a passive, wireless, chemical and biological sensor integrated with a wireless interrogation platform to monitor the sensor. The focus of this thesis is the realization of a wireless sensor interrogator capable of monitoring multiple, passive, resonant-frequency sensors. It is demonstrated, using Frequency Modulation Spectroscopy techniques, that the resonant frequency of a passive sensor can be detected and tracked over time. Simulated results are presented that verify the functionality of the proposed wireless sensor interrogator. In addition, an experimental hardware setup and subsequent experimental results are presented that verify the simulation results. Considerations for the design of the wireless sensor interrogator and opportunities for future research are discussed.